Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.50	8.121%	$226.5135	$226.51	$226.50	$226.50
Purchase #2	$78.30	9.103%	$85.4276	$85.43	$85.45	$85.40
Purchase #3	$141.71	8.452%	$153.6873	$153.69	$153.70	$153.70
Purchase #4	$128.42	13.836%	$146.1882	$146.19	$146.20	$146.20
Purchase #5	$202.54	9.259%	$221.2932	$221.29	$221.30	$221.30
Purchase #6	$94.98	10.734%	$105.1752	$105.18	$105.20	$105.20
Purchase #7	$185.47	13.394%	$210.3119	$210.31	$210.30	$210.30
7 purchase totals =	$1,040.92		$1,148.5969	$1,148.60	$1,148.65	$1,148.60